Merge #15163: Correct units for "-dbcache" and "-prune"

6f6514a080 Correct units for "-dbcache" and "-prune" (Hennadii Stepanov)

Pull request description:

  Actually, all `dbcache`-related values in the code are measured in MiB (not in megabytes, MB) or in bytes (e.g., `nTotalCache`).

  See: https://github.com/bitcoin/bitcoin/blob/master/src/txdb.h

  ba8c8b2227/src/init.cpp (L1405-L1424)

  Also, "-prune" is fixed:
  1. The GUI values in GB are translated to the node values in MiB correctly.
  2. The maximum of the "prune" `QSpinBox` is not limited by default value of 99 (GB).

  Fix: #15106

Tree-SHA512: 151ec43b31b1074db8b345fedb1dcc10bde225899a5296bfc183f57e1553d13ac27db8db100226646769ad03c9fcab29d88763065a471757c6c41ac51108459d

src/qt/forms/optionsdialog.ui

@@ -121,7 +121,7 @@
          <item>
           <widget class="QLabel" name="databaseCacheUnitLabel">
            <property name="text">
-            <string>MB</string>
+            <string>MiB</string>
            </property>
            <property name="textFormat">
             <enum>Qt::PlainText</enum>